1. Field of the Invention
This invention relates to a method of manufacturing high performance integrated circuit capacitors and/or resistors and the resulting capacitors and/or resistors.
2. Brief Description of the Prior Art
Integrated circuit capacitors, which are generally any two layers of electrical conductor with a dielectric therebetween, are generally disposed either (1) over active devices in the active device or moat regions of the entire integrated circuit, in which case the capacitors can be separate components or share structure with active components or (2) separated from the active device or moat region in which case such capacitors are generally disposed over the field oxide separating the active device or moat regions.
Integrated circuit capacitors as presently provided generally include either a portion of substrate silicon which has been highly doped or a highly doped polycrystalline silicon (polysilicon) layer with a dielectric thereover with the upper capacitor plate formed of metal, such as part of the metal interconnect or a thin (about 2K to 3K .ANG.) polysilicon film forming the upper plate. Such thin film polysilicon capacitor plates are difficult to dope to high dopant concentration and thus are not highly electrically conductive. The polysilicon films of such prior art capacitors are generally doped by ion implant or with phosphorous, generally POCl.sub.3. Consequently, the voltage coefficient of such capacitors tends to be poor in that the capacitor cannot hold its value when the bias thereacross changes due to the formation of space charge regions with the polysilicon. Also, when a low quality dielectric is used, the frequency performance is degraded. This limits the performance of the circuits that employ such capacitors as circuit elements.
High performance circuits which require linearity in the range of about 14 bits and higher generally require a precision capacitor. Such capacitors are of much higher quality than those generally fabricated in state of the art integrated circuits by the standard state of the art techniques.
It is therefore apparent that the quality of the capacitor plates and dielectric must be improved. To provide such improved capacitor plates in semiconductor material, it is necessary that the semiconductor material be very highly doped. However, a problem that arises is that the temperatures and duration required to provide the desired degree of doping in the present processing techniques disrupts the "thermal budget" (the time and temperature constraints which the circuit being fabricated can withstand without changing the electrical parameters of the circuit). It is therefore apparent that new processing techniques are required to provide capacitors of the quality required for the next generation of devices.